DE2363455A1 - DEVICE FOR SYNCHRONIZING AN OPTICAL SCANNER - Google Patents

Description

Boeblingen, December 13, 1973 pr-be

Applicant: 'International Business Machines

Corporation, Armonk, .N.Y. 10 504

Official file number: New registration File number of the applicant: LE 9-72-026

Device for synchronizing an optical scanner

The invention relates to a device for synchronization an optical scanner with a deflection element deflecting a light beam by angular rotation about a deflection point. In many fields of technology, especially in the field of data processing, so-called optical scanners are used, in which a sharply bundled light beam either through mechanically moved mirrors or by means of electro-optical or magneto-optical elements is periodically deflected to an object or a plane point and line in the manner of a To scan television raster. Such devices are used, for example, in optical printers, in optical character recognition and used in facsimile recording and reproduction. In German Offenlegungsschrift 2 250 763, a optical scanner described in which a laser to generate a bundled light beam and a rotating mirror for periodic Deflection of this light beam is used. When using an optical scanner for writing or reading of stored data, very precisely working clocks are required, which modulate the one that writes the data Synchronize the beam or precisely define the position of the beam scanning a certain area. In general becomes the synchronism between clock and movement

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of the beam is only made at the beginning of a line, while the synchronism when passing through the line is ensured by a high degree of constancy of the beam deflection. While this type of synchronization is sufficient for many applications, there are also cases, for example the use of a optical scanner for writing and reading data from an optical memory, v / o the required constancy of Beam movement can only be ensured in part and even then only with an extremely high level of technical effort can. For example, it is readily apparent that when a beam is deflected with the aid of a rotating polygon mirror not only mirrors with very precisely machined and aligned facets and a `` high ^ constancy of the mirror rotation, but also error-free ^ optical transmission systems and special constructive measures are necessary to ensure that the light spot generated by the beam in the scanning plane regardless of the respective angular position of the beam, the scanning plane sweeps over all areas at the same speed. But even if all these prerequisites are met, disturbances in the synchronism of the movement of the scanning beam, for example due to voltage fluctuations or due to vibrations transmitted to the scanner, not always with the data processing unit Systems required security are excluded.

The invention is based on the task, a simple one Specify synchronization device for optical scanners, with the help of which the position of the scanning beam within the individual Lines is defined at any time by synchronizing signals.

This object is achieved according to the invention by a device for synchronizing an optical scanner with one Light beam released by angular rotation around a deflection point deflecting deflection element, which is characterized by one in the area of the deflected beam arranged to the beam splitter

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Splitting of the beam into a scanning component and a synchronizing component moved synchronously with this, by an im A grid-like structure arranged in the area of this component having element and by a component that leaves the grid-like element and has two focal points optical element, in whose first focal point the deflection point of the deflecting element and in whose second focal point a light-sensitive element Element is arranged at its output, due to the modulation of the synchronizing component during passage the grid-like element produces an electrical, intensity-modulated synchronization signal.

Further features of the invention emerge from the subclaims in connection with the description.

The invention is explained in more detail below with reference to the figures. Show it: '

1 shows the schematic representation of an optical scanner,

Fig. 2 is a schematic representation of a

Exemplary embodiments of the invention for generating a synchronization signal,

3 shows the plan view of the folded beam path of a device according to FIGS. 1 and 2,

Fig. 4. a side view of that shown in FIG Contraption,

Fig. 5 is a plan view of another embodiment of the invention,

6 shows a side view of the device according to FIG. 5, LE 9-72-026 - 3 -

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7 shows the schematic representation of a further exemplary embodiment of the invention,

8 shows the block diagram of a device for recording data,

9 shows the schematic representation of a device for scanning and recognizing data.

In Fig. 1 a device for generating a scanning ■ light beam is shown. A light source 11 formed, for example, a is thrown onto a drum 38 via lenses 34, 31, a beam splitter 37 and a cutting edge 23. The cross section of the beam is adapted to the requirements of the modulator 21 with the aid of the lenses 17 and 19. The modulator 21 may, for example / an ^S known. be formed acousto-optical, electro-optical or magneto-optical modulator. It is set in such a way that the zero-order diffraction of the light beam is incident on the cutting edge 23 arranged in front of a recording surface 25 and the first-order diffraction is incident on this recording surface. The light beam therefore falls, depending on the control of the modulator 21, on the cutting edge 23 interrupting its path or on the recording surface 25. After leaving the modulator 21, the light beam reaches the lenses 27 and 29, which enlarge its cross-section. The required diameter of the beam leaving these lenses is determined by the size of the beam diameter required in the area of the lens 31. Since this lens is arranged in such a way that the smallest diameter of the light spot generated by it in the region of the recording plane 25 is limited by the diffraction, an increase in the diameter

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of the incident light beam is the diameter of the light spot generated in the area of the surface 25 is reduced. The ratio of the required diameter of the incident and exiting beam determines the focal lengths of lenses 27 and 29.

The beam emerging from the lens 29 passes through the cylinder lens 35 and falls on the rotating polygon mirror 33, the facets of which the beam across the width of the recording surface 25 turn. The number of mirror facets and the speed of rotation of the mirror determine the duration of a scan. These parameters are shared with the rotation speed of the recording area 25 is selected so that this recording area during a scanning time by the width of a picture element advances. -

The cylinder lenses 3.4 and 35 arranged on both sides of the polygon mirror 33 reduce the tolerance of the declination angle of the rotating mirror.

As can be seen from the foregoing, the Lens 31 around a projection lens with which a point with a diameter on the recording surface limited by the diffraction 25 is generated. Together with the cylinder lenses, it also reduces the declination tolerance. The focal length of the Lens 31 is determined by the scanning angle and the width of the recording surface 25.

A beam splitter 37 is arranged between the lens 31 and the cutting edge 23. Part of the beam penetrates it Beam splitter as a scanning component and, depending on the switching state of the modulator 21, either falls on the cutting edge 23 or onto the recording surface 25. The other part of the beam

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is reflected by the beam splitter as a synchronization component and arrives at the synchronization part to be described in more detail. The beam splitter can for example consist of a partially silver-plated mirror with an anti-reflective coating.

The recording surface 25 can, for example, consist of any photosensitive layer. In the present embodiment, it consists of the photoconductive Surface of a rotating drum 38. A photoconductive material suitable for such recording surfaces is for example, in U.S. Patent 3,484,237. The photoconductive material is in a manner known per se arranged over a conductive substrate, for example can consist of insulating material sprayed with aluminum.

The rotating drum 38 can according to the present embodiment Be part of a known electrostatic reproduction device. With these reproduction devices is carried out on the photoconductive recording material A corona discharge device first applied a uniform electrostatic charge * A subsequently applied to the Light beam impinging on the surface of the photoconductive material discharges the electrostatic charge at the contact point. the modulation caused by the modulator 21 when the photoconductive material is scanned in the direction of the arrow 39 by the light beam

creates a scanning track with an electrostatic pattern on the recording surface 25. Several such tracks or lines create an image which is subsequently developed with electrostatic toner to produce a visible image can be. The toned image can then be applied to a substrate such as e.g. paper, can be transferred in a known manner.

about the modulation of the light beam according to the position of the light beam To synchronize correctly on a scanning track, a part of the light beam is passed through the beam splitter 37 via a

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Synchronization path reflected. Fig. 2 shows schematically an optical system for generating a synchronization signal. To the For simplification, the light path is shown unfolded and the The reflection path generated by the beam splitter 37 of FIG. 1 is omitted. ■

The part of the light beam reflected by the beam splitter 37 of FIG. 1 passes through the rotating facet mirror 33 optical grating 51 and meets an elliptical mirror The optical grating is arranged so that the through the modulator 21 caused the beam deflection running on the synchronization path Beam deflects parallel to the direction of the lines of the optical grating. The elliptical mirror 53 is manufactured by Cut a desired section of an ellipse from an aluminum plate. The entire ellipse is dashed by the Line 55 shown. The ellipse has two foci, the first of which lies at the diversion point 57 (i.e. deflection point) of the mirror 33 and the second of which lies against a light-sensitive element 59. Light emanating from the diversion point 57 is thus transmitted through the elliptical mirror 53 onto the light-sensitive element 59 reflected. Since the light "scans" the optical grating 51 before it hits the elliptical mirror 53, that becomes the most photosensitive Element 59 received light intensity modulated, according to the position of the light beam on the optical Grating 51. The light falling on the light-sensitive element 59 is thus in accordance with the position of the light beam on its Scanning path intensity-modulated. With the output signal of the light-sensitive element one can thus determine the position of the light beam identify exactly within the scanning path.

In the schematic top view of FIG. 3, scanning path and Synchronization path shown. One of that shown in Fig.1 Laser beam source 11

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generated light beam 65 hits the rotating facet mirror 33 so that a reflected light beam 67 is thrown onto a scanning path in accordance with the rotational position of the mirror 33 will. The reflected light beam. 67 hits the beam splitter 37, which reflects about 25% of the light beam and about 75% passes through it leaves. The "radiation element 37 is arranged in such a way that the optical grating 51 and the recording surface 25 is the same distance from the beam splitter to have. The light beam 69 passing through the beam part 37 hits the recording surface 25 of the rotating drum 38 and continues to run along the scan path in the direction of arrow 39.

The light beam reflected by the beam splitter 37 falls on the surface of the optical grating 51 and runs over a synchronization path in the direction of the arrow 73 X does not reach the elliptical mirror. 53., Which shines this light on the light-sensitive element 59 reflected. Fig. 4 shows in a lateral schematic view of the optical system shown in FIG.

FIGS. 5 and 6 show a schematic plan view and side view, respectively another arrangement that. optical components for conducting Light on a scan path and a synchronization path. The generation of the scanning beam, its distribution on a scanning path

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and a synchronization path and the use of the beam traversing the scan path for data recording are the same as described in connection with FIGS. In the synchronization path, however, a lens 75 and a mirror 77 are also used. The lens 75 shortens the length of the scan of the optical grating 51 and thereby reduces its physical length. Such a reduction in the physical size of the grid is desirable if a document is to be scanned lengthwise and not widthwise with the scanning system. The mirror 77 directs the beam to the grating 51 and to the elliptical mirror 53. Although the lens 75 reduces the physical distance of the synchronization path, the point of diversion is still in the optical focus of the elliptical mirror 53.

Fig. 7 schematically shows another optical system for generation a synchronization signal. The mirror from the rotating facet 33 outgoing scanning light beam passes through the beam splitter 37 and the optical grating 51 as described above. Then the beam passes two elliptical, aspherical lenses 78 and 79 and is directed from there onto the light-sensitive element 59. The diversion point 57 is located in a focal point of the lens system and the light-sensitive Element 59 in the other. By using the

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elliptical lenses, the spherical deviation given with cylindrical lenses and thus the target size of the light * sensitive element 59 reduced. "....

Fig. 8 schematically shows a circuit diagram of a data recording arrangement. The circuit comprises the photosensitive element 59 and the modulator 21 of FIG. 1. In a conventional memory 81 standing data information is divided into rows of light and dark signals by a character generator 83. The character generator 83 speaks to digital information stored in memory 81 en and creates a character representation, in each case in form one scan line. Such a scan line can be done with conventional Decoding circuits are generated. · - -. · '... '·

The output signals of the character generator 83 are in parallel in a shift register 85 of a serial converter. The information is sequentially extracted from the shift register 85 to control the modulation of the scanning light beam, i.e. when the character generator supplies the output signals to the shift register 85, the information contained therein is sequentially to the The control unit of the modulator 21 is read out, thereby deflecting the beam. The sequential control for the shift register becomes

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Taken from the signal output of the light-sensitive element 59. The output signal of the element 59 is amplified and limited by an amplifier 87. The output signal of the Amplifier is doubled by a frequency multiplier 89. The frequency multiplier increases the distance between the Lines in the optical grating 51 of FIG. 6 allows. The frequency multiplier is not used if the resolution of the optical line grid matches that of the print.

The bit in the last position of the shift register 85 is shifted to the modulator 21 by the frequency multiplier and each subsequent bit in the register is shifted one position to the right. The output of the shift register controls the modulator 21 and this in turn controls the beam deflection according to the information content of the shift register pushed out bits. ·. . · '.

9 shows schematically a data recognition arrangement. These Arrangement is used in connection with a scanning light beam which is generated in a manner similar to that described in connection with FIG was and in connection with optical components for generating a Synchroni sationssignales similar to the description in

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Connection with Figures 2 and 4 is used. The system used to generate the scanning light beam closes. not necessarily the modulator -21 or the associated condensation optics, since here the generation of a continuous light beam over a scanned surface 101 is desired ; . . . ■■ · - · _.-.

By rotating the facet mirror 33, a scanning light beam is thus created which runs through the beam splitter 37 exactly as in the above description. Light passing the beam splitter travels on a scan path along surface 101 in the direction of arrow 103, accordingly the movement of the facet mirror 33. The surface 101 carries information, e.g. in the form of pressure. The one reflected from the surface 101 Light beam changes its intensity according to the information content at the point of impact of the beam. The reflected light beam will collected by a converging lens 105 and then hits the surface a photosensitive element 107. The output of this photosensitive element is detected by a threshold value detector 109, which has a binary output signal corresponding to the intensity of the light hitting the photosensitive element 107 supplies. The surface 101 is moved perpendicular to the scanning direction by a drive roller 103 to generate multiple scanning lines.

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The part of the scanning beam reflected by the beam splitter 37 runs through an optical grating onto the surface of a light- • sensitive element 59 exactly as it was described above in connection with FIGS. The output signal of the photosensitive element 59 is amplified and limited by the amplifier 87. Its output signal is used to make the binary Output of the threshold detector 109 into the shift register 111, i.e. the amplifier 87 delivers a pilot pulse corresponding to the resolution pattern of the optical grating with which the Output signal of the threshold detector 109 is transferred into the shift register. Each such pilot pulse stores a new data bit into the shift register 111 until it is several, a whole scan line contains representative data bits. -

The following is a description of various optical components that are used for the Arrangements shown schematically in FIGS. 1 to 4 can be used. . '..

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COMPONENT

Light source 11 PJanar mirror 13, 15 lens 17 Lens 19 Modulator 21 Lens 27 Lens 29 Lens 35 Mirror 33

Lens 34. . '

Lens 31
Beam guide 37
Optical line grid
Light sensitive element resolution
Lightening time
Processing speed of the recording surface 25 '

DESCRIBE'!

5 mW He-Ne laser 0.65mm 0, 1.7mrad Div. Front surface mirror 25 χ 25 mm plano-convex lens f = 25 mm, 12 mm plano-convex lens f = 10 mm, 8 mm acousto-optical deflector, Zenith M4OR plano-convex lens f = 8 ram, 4 mm plano-convex lens f = 38.1 mm, 20 mm cylindrical plano-convex lens I = 80mm, 25mm rotating mirror with 15 facets, facet angle scanning angle 18 °, drive 3552 rpm, 35.6mmj0T torodial planoconvex lens f = 43mm, 45 arcs planoconvex lens f = 352 mm, 30 χ 80 mm beam guide 19 χ 162 mm ■

Grid width 0.1 / 0.1mm lines, 13 mm high PIN 10 diode, 10 mm diameter of the light receiving surface 100 scans / cm 3.91 χ 10-5 sec 9.14 cm / see.

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"- 14 .-

In the above description, a light beam with a circular cross section is used accepted. In some systems, however, an elliptical point of light is desirable. The vertical dimension of the elliptical The point is determined according to the overlap tolerance that is necessary is to ensure a uniform light distribution between the scanning lines of the recording surface 25. the horizontal dimension is reduced by the amplitude of the synchronization output signal to improve.

For deflecting the light beam onto the scanning or synchronization path a rotating multi-facet mirror 33 was described in connection with FIG. It can of course various other deflection devices including rotating prisms or the like can be used. You can also other light sources and light modulation techniques can be used according to the speed requirements of the system. Of the Scanning light beam can be used both for data recording and for Data sampling can be used in the same machine by using an adjustable reflective surface between the beam splitter 37 and the recording surface 25 of Fig. 1 which moves to one position in which the main scanning beam is deflected to scan an area such as area 101 of FIG.

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Claims (11)

P A T E N TÄ N S P R Ü C H E CiJ Device for synchronizing an optical scanner with a deflecting element which deflects a light beam by angular rotation about a deflection point, characterized by a beam splitter (37) arranged in the area of the deflected light beam (67) for splitting the light beam into a scanning component (69) and one with this synchronously moving synchronizing component (71), by an element (51) arranged in the area of this component, having a periodic grid-like structure and by an optical element (53; 78, 79) having two focal points in its first, which component which leaves the grid-like element and which receives the component Focal point is the actual or virtual deflection point (57) of the deflection element (33) and in the second focal point of which a light-sensitive element (59/107) is arranged, at the output of which an electrical, intensity-modulated synchronization signal is generated. 2. Apparatus according to claim 1 with a light source and one in the beam path of the light source, movable arranged deflection element, which a light beam impinging on it at a deflection point on a scanning path deflects, characterized by a beam splitter (37) which is arranged in the scanning path (67) and which part of the beam (67) hitting it onto a scanning beam which leaves the beam splitter (37) undeflected (69) deflects an angle-forming synchronization path (71), a surface to be scanned (25, 101), which is arranged in the scanning path (69) and via which the scanning beam is caused by the movement of the deflection element (33) is guided back and forth, and a two-focal point, arranged in the synchronization path (71) j LE 9-72-026 - 16 - 409828/1004 optical element (53) whose first focal point corresponds to the actual odtJr & em. virtual deflection point (57) of the deflection element (33) 'coincides and a first light-sensitive element (59) is arranged in the second focal point and an optical line grating (51) is provided between the beam splitter (37) and the element (59), which all in such a way that the synchronizing beam separated from the deflected beam generates an intensity-modulated synchronizing signal when it passes over the line grating (51) at the output of the light-sensitive element (59). 3. Device according to claims 1 and 2, characterized in that that the deflection element (33) consists of a rotatably arranged polygon mirror. 4 «Device according to claims 1 to 3, characterized in that that between the beam splitter (37) and the surface (25) a cutting edge (23) such is arranged that the beam splitter (37) leaving the light beam as a function of its Modulation by the modulator (21) either interrupted by the ■ cutting edge or past it to the Surface (25) is won * 5. Device according to claims 1 to 4> characterized in that that the surface (25, 100) is perpendicular to the scanning movement caused by the deflecting element (33) of the light beam can be moved by a transport device (38, 108). 6. Device according to one or more of claims 1 to 5, characterized in that the optical element having two focal points consists of an elliptical Mirror (53) consists in one of the focal points LE 9-72-026. - l7 - '. 409828/100 4 it the photosensitive element (59) is arranged ^ eTPilitp weir · ^ kind, that all rays emanating from the other focal point of the elliptical mirror (53) on the light ^ sensitive element falling. 7. Device according to one or more of claims 1 to 5, characterized in that the optical element having two focal points consists of two cylindrical lenses (78, 79), in whose one focal point the photosensitive element (59) is arranged, in such a way that all proceed from the other focal point of the Lirisetis system Rays fall on the photosensitive element. 8. Device according to claims 6 or 7, characterized in that between the beam splitter (37) and the element having two focal points is a preferably a / s line grating, a periodic one Structure having element (51) is arranged. " '9. Device according to one or more of claims 1 to 8, characterized in that. reflected in the beam path of the surface to be scanned (1Ό1) Light a second photosensitive element (107) is arranged, the output of which is connected to a threshold value memory (109), which is its binary output signal supplies to a data register (111) which also contains the output signal of the first light-sensitive Element (59) is fed to a binary information bit in accordance with the binary value of the output signal of the second photosensitive element '(107) to store. 10. The device according to one or more of the preceding claims, characterized in that the photosensitive element (59) at least one LE 9-72-026 - 18 - ORIGINAL INSPECTED 409828/1004 .. Data register containing information bits (85, 111) is connected, the content of which can be read out by the output signal of the light-sensitive element (59) is. 11. The device according to claim 10, characterized in that the data register (85) with a light modulator (21) is connected, which the light beam generated by the light source (11) according to the information content of the or contained in the data register (85) Information bits modulated. -LE 9-72-026 - 19 - 409828/1004 XO Blank page